The present invention is directed to intraocular lenses (IOLs). More particularly, the invention relates to IOLs which have a plurality of optical powers and, in addition, are adapted to provide accommodating movement in the eye.
The human eye includes an anterior chamber between the cornea and iris, a posterior chamber, defined by a capsular bag, containing a crystalline lens, a vitreous chamber behind the lens containing the vitreous humor, and a retina at the rear of this chamber. The human eye has a natural accommodation ability. The constriction or contraction and relaxation of the ciliary muscle provides the eye with near and distant vision, respectively. This ciliary muscle action shapes the natural crystalline lens to the appropriate optical configuration for focussing light rays entering the eye on the retina.
After the natural crystalline lens is removed, for example, because of cataract or other condition, a conventional, monofocal IOL can be placed in the posterior chamber. Such a conventional IOL has very limited, if any, accommodating ability. However, the wearer of such an IOL continues to require the ability to view both near and far (distant) objects. Corrective spectacles may be employed as a useful solution. Recently multi-focal IOLs without accommodating movement have been used to provide vision correction.
Attempts have been made to provide IOLs with accommodating movement along the optical axis of the eye as an alternative to shape changing. Examples of such attempts are set forth in Levy U.S. Pat. No. 4,409,691 and several patents to Cumming, including U.S. Pat. Nos. 5,674,282 and 5,496,366. The disclosure of each of these patents is incorporated herein by reference. One problem that exists with IOLs which are adapted for accommodating movement toward and away from the retina of the eye is that such IOLs often cannot move sufficiently to obtain the desired accommodation because of space constraints within the eye. The present inventors are unaware of any so-called accommodating IOL which provides the desired degree of accommodation.
It would be advantageous to provide IOLs adapted for accommodating movement which can achieve an increased amount of accommodation with readily attainable amounts of accommodating movement.